/Engine/Source/Runtime/Engine/Public/ExternalTexture.h
UnregisterExternalTexture
bool GetExternalTexture ( const [FMaterialRenderProxy](API\Runtime\Engine\Materials\FMaterialRenderProxy) * MaterialRenderProxy, const [FGuid](API\Runtime\Core\Misc\FGuid) & InGuid, FTextureRHIRef & OutTextureRHI, FSamplerStateRHIRef & OutSamplerStateRHI )